Shaft centering assembly



July 7,1970 D. M. BAYLESS 3,519,083

SHAFT CENTERING ASSEMBLY Filed April 5, 1968 2 Sheets-Sheet 1 \NVENTOR DAVID M. BAYLESS wwwww ATTORNEY 2 Sheets-Sheet Filed April 5, 1968 J jd United States Patent 3,519,088 SHAFT CENTERING ASSEMBLY David M. Bayless, Sherman, Tex., assignor to G. W. Murphy Industries, Inc., a corporation of Texas Filed Apr. 3, 1968, Ser. No. 718,406 Int. Cl. E21c 5/11; F15b 15/14; F16i 15/50 US. Cl. 173-149 16 Claims ABSTRACT OF THE DISCLOSURE A fluid motor includes a piston and piston rod reciprocated within a cylinder by the action of pressurized fluid. One or more floating pistons are disposed about the piston rod for free movement within the cylinder in order to maintain the piston rod centered within the cylinder during reciprocation therein. Ports provide direct fluid communication between points on the wall of the cylinder which are spaced apart a distance greater than the width of a floating piston. The movement of a floating piston is thus arrested by the equalized pressures when the floating piston moves between the points on the wall of the cylinder.

FIELD OF THE INVENTION This invention relates to fluid motors, and more particularly to the use of floating pistons within a fluid motor cylinder to maintain a reciprocating piston rod centered within the cylinder during operation of the fluid motor.

THE PRIOR ART A large number of uses have been found for long stroke fluid motors, either hydraulic or pneumatic, wherein pressurized fluid reciprocates a piston and piston rod within a cylinder over a relatively long power stroke. An example of such use is a hydraulically operated earth auger in which a square kelly bar provides rotation to the auger and additionally serves as the shaft for a fluid motor which extends and retracts the auger. In order to drill deep holes in the earth with such augers, extremely long fluid cylinders are necessary to allow a long stroke of the kelly bar.

However, the long fluid cylinders used on some units have caused problems in that the kelly bar tends to be laterally deflected from the longitudinal axis of the cyllinder during the extremely long strokes. This deflection not only reduces the accuracy of the drilling of the hole, but induces undue strain on the kelly bar. Additionally, the lateral deflection, or whipping, of the kelly bar sometimes causes scoring of the inside bore of the cylinder when the kelly bar is rotated.

SUMMARY OF THE INVENTION In accordance with the present invention, floating pistons are disposed about the reciprocating shaft of an elongated fluid motor for freely moving within the cylinder along the length of the shaft to maintain the shaft in a centered position within the cylinder. Ports provide direct fluid communication between spaced points on the wall of the cylinder to arrest the movement of the floating piston at predetermined locations in the cylinder in order to limit the length of travel of the floating pistons.

DESCRIPTION OF THE DRAWINGS For a more complete understanding of the present invention and for further objects and advantages thereof, reference may not be had to the following description taken in conjunction with the accompanying drawings, in which: 1

FIG. 1 is a perspective view of an earth drilling rig utilizing the present invention;

3,519,088 Patented July 7, 1970 FIGS. 2-4 are longitudinal sectional views of a piston and cylinder assembly according to the invention in various operational stages; and

FIG. 5 is a cross sectional view of the cylinder shown in FIG. 2 taken generally along the lines 55.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 discloses a typical hydraulic drilling rig designated generally by numeral 10 which is mounted upon a vehicle 12. The drilling rig comprises an elongated vertical cylinder 14, only a portion of which is shown, which reciprocates an elongated square kelly bar 16 over a long power stroke. An auger 18 is mounted on the end of kelly bar 16. A turntable 20 rotates the kelly bar 16 to dig with the auger 18 in the manner illustrated. In order to dig deep holes, the kelly bar '16 is required to make extremely long strokes, thus requiring a long hydraulic cylinder 14.

FIG. 2 is a somewhat diagrammatic sectional view of the hydraulic cylinder 14 wherein the kelly bar 16 is fully retracted within the cylinder 14. A piston 22 is connected to the upper end of the kelly bar 16 and closely fits within the interior of the cylinder 14. Fluid ports 24 and 26 are disposed in the ends of cylinder 14 to allow the selective admission and exhausting of pressurized hydraulic fluid by suitable structure not shown. The hydraulic fluid acts upon the piston 22 to selectively reciprocate the piston 22 and the kelly bar 16. Seals 28 are provided about the piston 22 to seal with the inner walls of the cylinder 14.

A first floating piston 30 is disposed within the cylinder 14 about the kelly bar 16. Floating piston 30 has a cylindrical outer surface in frictional contact with the inner surface of the cylinder 14, with seals 32 providing a fluid seal between the piston 30 and the inner 'walls of the cylinder 14. The floating piston 30 has a substantially square passageway through the center thereof to closely receive the square kelly bar 16. Seals 34 provide a fluid tight seal between the piston 30 and the kelly bar 16.

A ball check valve 36 is provided in the piston 30 to prevent excessive fluid pressure buildup on the upper end of the piston 30. Angular projections 38 are provided on both faces of the floating piston 30 for reasons to be later described. Fluid bypasses 40 provide continuous direct fluid communication between spaced points along the length of the fluid cylinder 14. As will be later described in greater detail, fluid bypasses 40 tend to arrest the movement of the piston 30 when piston 30 moves to the position shown in FIG. 2.

A second floating piston 42 has a cylindrical outer surface including seals 44 which sealingly engage the inner surface of the cylinder 14. As best shown in FIG. 5, floating piston 42 has a substantially square hole through the middle thereof for reception of kelly bar 16. Seals 46 provide a fluid tight seal between the piston 42 and the kelly bar 16. A channel is disposed through the piston 42 with a ball check valve 48 therein to prevent excessive buildup of fluid pressure on the upper side thereof. Annular projections 50 (FIG. 5) are provided on the lower side of the piston 42. Fluid bypasses 52 provide continuous fluid communication between spaced points along the cylinder 14.

From the drawing, it may be seen that the width of the floating piston 42 is less than the width of the floating piston 30. Correspondingly, the distance between the spaced apart openings of the fluid bypasses 52 is less than the distance between the openings in the fluid bypasses 40.

In operation of the fluid motor, the floating pistons 30 and 42 move along selected lengths of the cylinder 14 to provide constant centering and support to kelly bar 16.

As the kelly bar 16 is moved to the fully retracted position shown in FIG. 2, fluid under pressure admitted through port 24 is transmitted through the bypasses 52 and 40 to the underside of piston 22. The floating pistons 42 and 30 are trapped between the openings of the respective bypasses 52 and 40 due to the equalization of pressure on both sides of the pistons. When the turntable 20 rotates the kelly bar 16, the floating pistons 42 and 30 rotate within cylinder 14 to maintain the kelley bar 16 centered within the cylinder 14.

When fluid is admitted under pressure through the port 26, the pressure of the fluid forces the piston 22 downwardly, thereby causing the kelly bar 16 to be extended from the cylinder 14. As the piston 22 travels downwardly, the underside of piston 22 comes into contact, with the annular projections 38 of the first floating piston 30. The downward force exerted by the piston 22 is suflicient to dislodge the piston 30 from between the spaced apart openings of the bypasses 40, and the piston 30 is carried downwardly as shown in FIG. 3.

The spring loaded ball check valve 36 is opened to allow passage of fluid through the piston 30 in case of unusual pressures exerted on the system, to prevent excessive intensification of fluid pressure within the cylinder 14. The projections 38 enable the piston 22 to contact the floating piston 30 without first blocking off one of the ports of the bypasses 40 and thereby creating excessive pressures within the cylinder 14. When the piston 22 is near the midpoint of the cylinder 14 (FIG. 3), the floating piston 42 provides a centering support to the bar 16 to prevent lateral displacement of the bar.

Upon continued application of fluid under pressure through the port 26, the piston 22 is depressed further downwardly in the cylinder 14. Piston 22 carries the first floating piston 30 downwardly until projections 38 or piston 30 contact the second floating piston 42 and move the piston 42 to the position shown in FIG. 4. Projections 38 enable piston 42 to be moved from between the fluid communication ports of the bypasses 52 without blocking the bypass of fluid around the piston 42, thereby enabling the piston 42 to be more easily moved from its rest position. As shown in FIG. 4, in the extended position of the kelly bar 16, the floating pistons 30 and 42 provide a centering support to the portion of the kelly bar 16 still within the cylinder 14. The ball check valve 48 in piston 42 may be opened to relieve excessive fluid pressure within cylinder 14.

When fluid under pressure is again admitted through the port 24, the fluid exerts an upward force on floating piston 42 and carries the pistons 42, 30 and 22 upwardly. It will be noted from an inspection of FIG. 4, that the projections 50 extending from the floating piston 42 prevent the piston 42 from sealing against the port 24 and thereby preventing the admission of fluid therethrough. The three pistons are moved upwardly until the second floating piston 42 reaches the position shown in FIG. 37

As the floating piston 30 is longer than the bypasses 52, floating piston 30 is not stopped by the bypasses 52. However, the second floating piston 42 is stopped by the bypasses 52 due to the equalization of pressure on both sides of the piston 42. Fluid under pressure is then admitted through the port 24 and through the bypasses 52 to force piston 22 and floating piston 30 upwardly until the floating piston 30 is stopped in the position shown in FIG. 2 by the bypasses 40.

The travel of floating piston 30 is arrested due t the equalization of pressure on either side of the piston caused by the direct fluid communication provided by bypasses 40 between spaced points on the cylinder 14. The projections 38 space piston 22 from said piston 30 to allow fluid to flow through the bypasses 40 around the piston 30 to push piston 22 to the upper position shown in FIG. 2.

When the piston 22 and the traveling pistons 30 and 42 are being moved upwardly into cylinder 14, the spring loaded check valves 36 and 48 remain closed. Although the velocity of the kelly bar 16 tends to carry the floating pistons 30 and 42 past the bypass areas due to friction of the piston seals against the kelly bar, this tendency is counteracted by the frictional resistance of the floating piston seals against the walls of the cylinder 14.

The present invention provides an apparatus for maintaining the centering of a piston shaft within an elongated cylinder during reciprocation of the shaft within the cylinder. Further, the present invention provides apparatus for preventing excessive lateral deflection of an elongated shaft Within a cylinder to keep the shaft from scoring the inside of the cylinder and to enable accurate rotation of a shaft about its longitudinal axis.

Whereas the present invention has been described with respect to specific embodiment thereof, it is to be understood that various modifications and changes may be suggested to one skilled in the art, and it is intended to cover such modifications and changes in the appended claims.

What is claimed is:

1. In apparatus wherein fluid reciprocates a piston and piston rod within a cylinder, the combination comprising:

(a) floating piston means disposed about said piston rod for movement within said cylinder along a length of said piston rod to maintain the centering of said piston rod Within said cylinder, and

(b) means providing direct fluid communication between points spaced along the length of said cylinder for arresting the movement of said floating piston means when said floating piston means moves between said points.

2. The combination of claim 1 wherein said floating piston means comprises a ring-like structure with an inner surface disposed about said piston rod and an outer surface having frictional contact with the interior wall of said cylinder.

3. The combination of claim '2 and further comprising:

check valves in said ring-like structure which are opened by fluid pressure only when said piston is moving in a preselected direction in said cylinder.

4. The combination of claim 1 and further comprising:

meansto rotate said piston, piston rod and floating piston means within said cylinder.

5. The combination of claim 4 wherein said piston rod has a square cross section.

6. The combination of claim 1 wherein said piston means comprises:

a plurality of floating pistons slidably mounted around said piston rod and operable to move between one end portion of said cylinder and positions spaced along the length of said piston rod.

7. The combination of claim 6 and further comprising:

a plurality of means providing direct fluid communication being disposed along the length of said cylinder.

8. A fluid motor comprising:

(a) a cylinder having inlet and outlet ports for selectively receiving pressurized fluid,

(b) a piston reciprocatable within said cylinder by pressurized fluid,

(c) a shaft connected at one end to said piston for reciprocation along the longitudinal axis of said cylinder,

(d) a plurality of floating piston means disposed about said shaft for free travel along a length of said shaft within said cylinder to maintain said shaft in a centralized position within said cylinder, said floating piston means adapted to abut one another in an end portion of said cylinder and being movable from the abutting position to spaced apart locations along said shaft,

(e) means for arresting the movement of each said floating piston means at a different predetermined location in said cylinder, and

(f) means for rotating said shaft about the longitudinal axis thereof during operation of the motor.

9. The fluid motor of claim 8 wherein said floating piston means comprises two hollow pistons slidably mounted about said shaft.

10. The fluid motor of claim 9 wherein one of said hollow pistons is movable along a first length of said cylinder and the other of said hollow pistons is movable along a second length of said cylinder which is shorter than said first length, said second length being common with said first length.

11. A fluid motor comprising:

(a) a cylinder having inlet and outlet ports for selectively receiving pressurized fluid,

(b) a piston reciprocatble within said cylinder by pressurized fluid,

(c) a shaft connected at one end to said piston for reciprocation along the longitudinal axis of said cylinder,

(b) a piston reciprocatable within said cylinder by for free travel along a length of said shaft within said cylinder to maintain said shaft in a centralized position within said cylinder,

(e) port structure providing direct fluid communication between spaced points in the wall of said cylinder for arresting the movement of said floating piston means at a predetermined location in said cylinder, and

(f) means for rotating said shaft about the longitudinal axis thereof during operation of the motor.

12. The fluid motor of claim 11 and further comprising:

two port structures spaced along said cylinder, each of said port structures defining an end of one of said first and second lengths of said cylinder along which said hollow pistons are movable.

13. The fluid motor of claim 12 wherein said two hollow pistons have different widths.

14. The fluid motor of claim 13 wherein said two port structures provide fluid communication between two pairs of spaced points in the walls of said cylinders, said pairs of spaced points having different spacing intervals whereby the movement of each of said hollow pistons is arrested at a location between a particular pair of spaced points.

15. The fluid motor of claim 14 wherein said pair of spaced points having the shortest spacing intervals defines the end of the shortest length of said cylinder along which one of said hollow pistons is movable.

16. The fluid motor of claim 15 wherein the cross section of said shaft is square.

References Cited UNITED STATES PATENTS 787,480 4/1905 Tanner 92-65 XR 1,063,360 6/1913 Larsen 91-181 XR 2,124,609 7/1938 Dickenson 173-152 XR 2,148,616 2/1939 Gruber 91-189 XR 2,193,125 3/1940 Evans et a1. 91-189 2,577,462 12/1951 Hackney 91-181 XR 2,764,131 9/1956 Knights 91-167 XR 2,847,188 8/1958 Wiltse 173-150 2,856,155 10/1958 Putt 173-150 2,898,084 8/1959 Eckel et a1. 173-149 3,190,077 6/1965 Scholin 91-399 XR MARTIN P. SCHWADRON, Primary Examiner L. J. PAYNE, Assistant Examiner US. 01. X.R.

g g UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 519 O 88 Dated July 7 1970 Inventor(s) David M. Bayless It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

C01. 3, line 9, "kelley" should be -kel1y-;

line 15, delete after "contact".

Col. 5, line15, "reciprocatble" should be -reciprocatab1e--;

line 20, "(b) a piston reciprocatable within said cylinder by" should be -(d) a floating piston means disposed about said shaft- SIGNED Aim QEAL) Attcat:

Ed a M. nmhmln.

mm 1:. sown-m, m. Mtcsung Officer flomissioner of Patents 

